1. Field of the Invention
The present invention relates to a rotary pump which is used as, for example, a fuel pump of a micro-gas turbine, etc. and more specifically to an improvement in a rotary pump which is equipped in a casing with partition plates (vanes) that contact the rotor.
2. Prior Art
This type of rotary pump is disclosed in, for example, Japanese Patent Application Publication (Kokoku) No. 35-18115, Japanese Utility Model Application Laid-Open (Kokai) No. 48-113011, Japanese Patent Application Laid-Open (Kokai) No. 49-112209, Japanese Utility Model Application Laid-Open (Kokai) No. 50-115205, Japanese Patent No. 2980628 (Japanese Patent Application Laid-Open (Kokai) No. 3-206382) and Japanese Patent Application Laid-Open (Kokai) No. 8-21389.
Such rotary pumps are basically comprised of: a casing which has a circular inner circumferential surface, a rotor which rotates about the center of the inner circumferential surface of the casing as the central axis, a partition plate which is installed so as to be movable in and out of the casing with the tip end being able to come into contact with outer circumferential surface of the rotor, a spring which drives the partition plate so that the partition plate is in constant contact with the rotor, an intake port which is formed in the casing and is positioned after the partition plate with respect to the direction of rotation of the rotor, and a discharge port which is formed in the casing and is positioned before the partition plate with respect to the direction of rotation of the rotor.
In pumps of this type, when the rotor is rotated, the fluid that is to be handled is taken in through the intake port, pressurized by being constricted by the inner circumferential surface of the casing, the rotor and the partition plate, and then discharged from the discharge port. In this case, the partition plate is driven by the elastic force of the spring so that the partition plate is maintained in constant contact with the rotor, and the partition plat is moved in and out of the casing while sliding along the casing.
In the United States, diesel oil (light oil) is used as a fuel in the fuel pumps of micro-gas turbines in accordance with ASTM (US standards). In Japan, to the contrary, kerosene is used in most cases.
However, while diesel oil has a high viscosity and considerable lubricating properties, kerosene has a low viscosity and provides little lubrication.
Accordingly, in the case of rotary pumps that use a low-viscosity fuel oil such as kerosene, etc. as the fluid being handled, the fluid being handled is interposed in the areas of sliding movement between the casing and the partition plate. However, on the intake side in particular, there is no direct inflow of a compressed fluid being handled though such flow occurs on the discharge port side; as a result, wear becomes conspicuous. Consequently, the useful life of the partition plate, which is manufactured from a relatively soft material compared to the material for the casing, is short; and a drop in pump performance occurs after approximately three months (1000 hours of operation).
In some cases, gear pumps are used as fuel pumps in order to avoid this problem. However, in such cases, the increase in cost presents difficulties.
The present invention was devised in light of the above-described problems and was created in order to solve these problems. The object of the present invention is to provide a rotary pump that has an extended useful life with a simple structure and at a low cost.
The present invention is for a rotary pump that includes: a casing which has a circular inner circumferential surface, a rotor which rotates about the center of the inner circumferential surface of the casing as the central axis, a partition plate which is installed so as to be movable in and out of the casing with its tip end being able to come into contact with outer circumferential surface of the rotor, a spring which drives the partition plate so that the partition plate is in constant contact with the rotor, an intake port which is formed in the casing and is positioned after the partition plate with respect to the direction of rotation of the rotor, and a discharge port which is formed in the casing and is positioned before the partition plate with respect to the direction of rotation of the rotor; and in the rotary pump of the present invention, it is characterized in that a communicating portion that communicates between the intake port side and the discharge port side is formed in the partition plate.
When the rotor is rotated, the fluid to be handled is taken in through the intake port, pressurized as a result of being constricted by the inner circumferential surface of the casing, the rotor and the partition plate, and then discharged from the discharge port. In this case, since the partition plate is driven by the elastic force of the spring so that the partition plate is maintained in constant contact with the rotor, the partition plate is moved in and out of the casing while sliding along the casing.
The fluid being handled is interposed in the areas of sliding movement between the casing and the partition plate so that these areas are lubricated. The portions of the areas of sliding movement between the casing and partition plate that are located on the discharge port side are well lubricated because the pressurized fluid being handled flows in from the discharge port. The portions of the areas of sliding movement between the casing and partition plate that are located on the intake port side can be well lubricated also because the pressurized fluid being handled is caused to flow in through a bypass route around the partition plate and is also caused to directly flow in through the communicating portion formed in the partition plate. Accordingly, high lubrication is obtained in the areas of sliding movement between the casing and the partition plate on both the intake port side and discharge port side, thus eliminating concern about wear.
Since it is only necessary to form the communicating portion in the partition plate, the pump of the present invention can be provided at low cost by simple machining.
It is preferable that the communicating portion be a single small hole with a diameter of 0.2 to 0.5 mm. With this structure, a good flow-through action is expected in cases where the fluid being handled is a low-viscosity fuel oil such as kerosene, etc., so that smooth lubrication is possible.
It is also preferable that the communicating portion be formed so that this communicating portion communicates with the discharge port alone, only at a time other than the time when the partition plate""s protruding amount is the minimum. With this structure, only at a time other than the time of minimum protrusion of the partition plate, e.g., only at the time of maximum protrusion of the partition plate, the pressurized fluid being handled on the discharge port side will pass through the communicating portion and be introduced into the areas of sliding movement on the intake port side. Accordingly, the lubrication of these areas can be quickly accomplished, and there is no hindrance of the inherent partitioning function of the partition plate.
It is further preferable that the rotor have a substantially equilateral-triangular shape that makes a sliding contact with the inner circumferential surface of the casing. Furthermore, it is also preferable that two partition plates be installed so as to face each other on a straight line which passes through the center of the rotor and that two intake ports and two discharge ports be provided. With this structure, the pump is constructed as an equilibrium type rotary pump, the pressure balance can be uniform, and the pressure cycle can be smoothed.
It is further preferable that the spring have a semi-annular shape and both ends of the spring be engaged with the base portions of the respective partition plates. With this structure, since a single spring can be used, the number of parts required is reduced, the structure is simplified, and the cost is reduced.